Source-based knowledge is drawn from historical sources in the sense of sources for a given problem. There is, however, a general concept of historical source in addition to that restricted to a given issue.¹ The general concept is used by historians when they try to define a historical source in general. E. Bernheim gave two different definitions of a historical source, the first of which has so far been disregarded (except by J. Giedymin); it refers to sources in general as "the material from which our science draws cognition".² The second, more expanded, says that sources are "results of human activity which either by their very destination or by their very existence, origin or other circumstances are particularly suited to inform about and to verify historical facts".³ A similar definition is given by many German scholars who in that respect follow Bernheim quite obviously.⁴ Ch. V. Langlois and Ch. Seignobos follow their famous statement that "l"histoire se fait avec de documents"by the formulation that "they are traces left by human thought and needs in the past (d"autre-fois)".⁵